The armature movement of an actuator, in particular an electromagnetic actuator, used for moving a control element back and forth coincides with the movement of the control element, making it possible to detect the armature movement and thus also the control element movement for the actuator operating range.
With an electromagnetic actuator having two spaced-apart electromagnets with oppositely arranged pole faces, between which an armature subjected to an alternating current is guided back and forth counter to the force of restoring springs, the armature movement can be inferred from the current and/or voltage values detected at the respectively capturing magnet and/or the respectively holding magnet upon release, and the detected values can be used for triggering purposes, following a corresponding signal processing.
An electromagnetic actuator of this type is used, for example, in the form of a fully variable valve actuator for triggering a gas cylinder valve on an internal combustion engine. Detecting a movement by inferring it from the current and voltage courses at the electromagnet coils is no longer sufficient to meet the higher requirements for triggering accuracy, particularly with respect to influencing the impact speed between armature and pole face of the respective capturing magnet, and thus also for the valve seating speed at the valve seat, because the signals obtained in this way cannot be converted for use until the following stroke cycle.
For that reason, the armature movement and thus also the control element movement must be detected “online” and over the complete stroke length by a corresponding sensor, so as to influence the current flow to the electromagnets during the control element movement by means of signals which correspondingly trigger the actuator, e.g. an electromagnetic actuator, so that the armature movement can be guided even during the current stroke cycle.
This requirement can be met with just one distance-measuring sensor which generates a signal during the complete stroke movement, meaning it “plots” the stroke path, wherein the sensor should be protected as much as possible against interference because of the resolution and accuracy requirements for gas cylinder valves, but also injection nozzles and needle valves, due to the relatively short stroke distances. The same is also true for other applications where the movement of a back and forth moving component, e.g. a piston movement or the like, must be detected with high accuracy.
A sensor of this type is known in principle from German patent document DE 101 57 119 A, but requires a relatively long structural length if precise measuring signals are desired.